The field of the disclosure relates generally to gas temperature measurement, and more specifically, to methods and a system for measuring gas temperature in harsh environments based on radiation thermometry using thin filaments embedded within robust outer hollow filaments.
At least some known turbomachines, such as gas turbine engines, include a plurality of rotating turbine blades or buckets and stationary nozzle segments that channel high-temperature fluids, i.e., combustion gases, through the gas turbine engines. Many of these known gas turbine engines include temperature monitoring systems that provide operational temperature data in real time, i.e., at the time of measurement. Measuring gas temperatures in a combusting flame or harsh environment downstream of a combustor, i.e., a hot gas path may include many sources of inaccuracy and non-repeatability. Many of those relate to physical properties of the temperature measurement mechanisms positioned in or proximate the flow of the hot combustion gases and/or proximate the high-temperature gas turbine components. For example, such detection mechanisms include water-cooled thermocouple rakes and gas sampling/thermal radiation probes for point temperature measurements. However, these temperature measurement mechanisms do not account for radiation effects prominent in the hot gas path. Also, due to the low spatial resolution features and the low accuracy associated with measuring boundary layer temperature profiles, these temperature measurement mechanisms do not provide accurate temperature distribution profiles and alternative computational extrapolations and approximations must be used to facilitate spatial-resolution of the temperature profiles, albeit, with some inaccuracies induced by the modeling techniques and approximations used. In addition, due to the high temperatures in the hot gas path and the short service life of the thermocouple wires in such high-temperature environments, the water-cooled thermocouple rakes require a significant amount of water cooling for the necessary additional infrastructure to reduce accelerated wear on the associated fluid transport features. Therefore, the water-cooled thermocouple rakes cannot be operated indefinitely at high power conditions. Also, the additional cost of the water-cooling features in hardware, installation, and maintenance could be significant. At least some other known temperature measurement mechanisms include laser diagnostic techniques, e.g., laser Rayleigh scattering, laser Raman scattering, and planar laser induced fluorescence. However, these temperature measurement mechanisms are difficult to implement for temperature control of the gas turbine engine.
Therefore, to overcome the deficiencies of known temperature measurement mechanisms with respect to gas temperature profiles and near-wall temperature measurements in high-temperature and high-pressure environments, gas turbine manufacturers may elect to fabricate, install, and run hot gas components with greater thermal margins to extend the useful service life of such components. Increasing thermal margins typically manifests as increased wall thicknesses and other ruggedizing methods. Such increased ruggedness of those components increases the costs of production and increases a potential for premature reductions in service life due to excessive temperature profiles induced in the walls of the components during operations that typically include large-scale temperature changes, e.g., startups, shutdowns, and load changes. Increasing thermal margins during gas turbine operation is typically manifested as increased cooling flow rates for those components. Increased cooling flow usage for those components increases the fuel consumption and decreases gas turbine efficiency.